How about this:
http://www.nitue.net/#fcp/direct!id=7542The way I see it is, If you don't have PE, you cant see anybody, but with sneak, noone can see you!
10 AP so you only have to wait a second or two but with silent death and hth Criticals theres a very good chance you're target is knocked out and cold. You said you wanted crippling I though finesse would be a good choice but maybe you can lower the luck to 8 or 6 in case you want alittle bit more resistance.
95% chance to critical eyes, 85% for head, and 65% for arms.
also, you can talk like a normal human being which is always good

no need for drugs, but you can modify it to as how you see fit like 1 str = 8 end